Because I've noticed a couple of references in other projects' bugs: I'm already working on this and don't anticipate that it will be super difficult. I will be adding support back to 2.7 (but probably stopping there). I have future-import parsing working as well, which is necessary for print statements and barry_as_FLUFL handling.

https://github.com/thatch/python-grammar-changes has a hand-compiled list of what changed, but I hope to create snippets and mechanically verify what versions they work on as well.